Can we use read-modify-write instruction such as BSET and BCLR

Question:

The manual describes some bits as follows: "Nothing is assigned. In an attempt to write to these bits, write "0". The value, if read, turns out to be indeterminate." For other bits that are assigned to the same address with the above bits, can we use read-modify-write instructions such as BSET and BCLR?

Answer:

There is no difference in the operation of an unassigned bit whether you program a "0" or "1". However, these bits may be assigned for new functions in future expansions, which is why the user's manual advises you to program these bits with "0". You can use instructions such as BSET and BCLR, but you should write "0" to these bits when you program an immediate value directly.